Deletion of porcine BOLL causes defective acrosomes and subfertility in Yorkshire boars

SummaryA recessively inherited sperm defect of Finnish Yorkshire boars was detected more than a decade ago. Affected boars produce ejaculates that contain many spermatozoa with defective acrosomes resulting in low fertility and small litters. The acrosome defect was mapped to porcine chromosome 15 but the causal mutation has not been identified. We re-analyzed microarray-derived genotypes of affected boars and performed a haplotype-based association study. Our results confirmed that the acrosome defect maps to a 12.24 Mb segment of porcine chromosome 15 (P=3.38 × 10−14). In order to detect the mutation causing defective acrosomes, we sequenced the genomes of two affected and three unaffected boars to an average coverage of 11-fold. Read-depth analysis revealed a 55 kb deletion that segregates with the acrosome defect. The deletion encompasses the BOLL gene encoding the boule homolog, RNA binding protein which is an evolutionarily highly conserved member of the DAZ (deleted in azoospermia) gene family. Lack of BOLL expression causes spermatogenic arrest and sperm maturation failure in many species. Our study reveals that absence of BOLL is associated with a sperm defect also in pigs. The acrosomes of boars that carry the deletion in the homozygous state are defective suggesting that lack of porcine BOLL compromises acrosome formation. Our findings warrant further research to investigate the precise function of BOLL during spermatogenesis and sperm maturation in pigs.

PROLACTIN RECEPTOR GENE (PRLR) ROLE IN SWINE REPRODUCTION

PRLR gene has been studied as a candidate gene for litter size in swine because of prolactin biological functions and their association with reproduction. Prolactin receptor gene is mapped on porcine chromosome 16. The established PCR-RFLP polymorphism at PRLR locus demonstrated the presence of two alleles, А and В and three genotypes АА, АВ and ВВ. There were found different allele and genotype frequencies in different pig populations with variation of the effects of PRLR genotypes on litter traits. Additional studies should be done in specific breeds and populations to evaluate the association of existing PRLR locus polymorphism with reproductive traits before application of marker-assisted selection in these populations.

Assignment for genes encoding the terminal complement components to porcine chromosome

One of the major goals of the porcine genome projects is building a physical map. To assign the porcine genes encoding the complement components C6, C7, C8 and C9 to porcine chromosomes, we used a porcine 7000Rad Radiation Hybrid panel (IMpRH) containing 118 clones provided by INRA-University of Minnesota. It resulted in assignment of the porcine C6, C7 and C9 genes to chromosome 16q1.4, the porcine C8A and C8B genes to chromosome 6q3.1-q3.5 as well as the porcine C8G gene lonely to chromosome 1q2.13.

Isolation and physical localization of new chromosome-specific centromeric repeats in farm animals

In this study, new classes of tandemly repeated DNA sequences in the centromeric regions of three farm animal species are reported. Pericentromeric regions of bovine chromosome X, porcine chromosome 14 and equine chromosome 1 were microdissected by laser and amplified by DOP-PCR. Painting probes showed strong hybridization signals on their corresponding centromeres. Specific DNA fragments were isolated by cloning and sequenced. For each species, high homology level was found among the sequences. The presence of specific repeats within each sequence allows us to consider them as monomeric units or parts of longer tandemly repeated monomeric units that generate a specific higher-order repeat. In this respect, the isolation of new centromeric sequences enriches the genetic map of these three species and represents a useful tool for FISH analysis, thus expanding our knowledge on centromeres of farm animal species.

Characterization, Tissue Expression, and Imprinting Analysis of the Porcine CDKN1C and NAP1L4 Genes

CDKN1C and NAP1L4 in human CDKN1C/KCNQ1OT1 imprinted domain are two key candidate genes responsible for BWS (Beckwith-Wiedemann syndrome) and cancer. In order to increase understanding of these genes in pigs, their cDNAs are characterized in this paper. By the IMpRH panel, porcine CDKN1C and NAP1L4 genes were assigned to porcine chromosome 2, closely linked with IMpRH06175 and with LOD of 15.78 and 17.94, respectively. By real-time quantitative RT-PCR and polymorphism-based method, tissue and allelic expression of both genes were determined using F1 pigs of Rongchang and Landrace reciprocal crosses. The transcription levels of porcine CDKN1C and NAP1L4 were significantly higher in placenta than in other neonatal tissues (P<0.01) although both genes showed the highest expression levels in the lung and kidney of one-month pigs (P<0.01). Imprinting analysis demonstrated that in pigs, CDKN1C was maternally expressed in neonatal heart, tongue, bladder, ovary, spleen, liver, skeletal muscle, stomach, small intestine, and placenta and biallelically expressed in lung and kidney, while NAP1L4 was biallelically expressed in the 12 neonatal tissues examined. It is concluded that imprinting of CDKN1C is conservative in mammals but has tissue specificity in pigs, and imprinting of NAP1L4 is controversial in mammalian species.